Conventionally, with a dome-type camera, it is known that a slight difference occurs in optical path lengths of light passing through a dome cover due to subtle unevenness in the thickness of the dome cover, resulting in increased aberration, which then causes a slight blur in an image captured by a camera lens (for example, see Patent Literature 1). This blur is more noticeable in a low tilt angle image (an image obtained by capturing the horizontal direction of the dome cover), but a conventional dome-type camera is of an image quality of a VGA (640×480 pixels) class and the image quality of such a conventional dome-type camera is not so high, and thus, a slight blur is not considered a problem.
However, in recent years, the image quality of a dome-type camera is ever more improved, and a dome-type camera of an image quality of a megapixel (1280×960 pixels) class (also referred to as a megapixel dome camera) is being developed. With such a megapixel dome camera, a slight blur, which would not be a problem with a conventional VGA dome camera, is an issue of image quality deterioration. Thus, conventionally, development of a technology for improving the image quality of a megapixel dome camera is desired.